Field of the Invention
The present invention relates to a temperature regulating apparatus that regulates the temperature of a first medium by performing heat exchange between the first medium and a second medium via a heat exchanger, an exposure apparatus including the temperature regulating apparatus, and a method of manufacturing a device using the exposure apparatus.
Description of the Related Art
Recently, an exposure apparatus for manufacturing devices, such as semiconductor devices, has been required to have high productivity. Along with this requirement, the power consumption tends to increase. On the other hand, device patterns to be formed decrease in size more and more, and hence, it is necessary to maintain the environment in the exposure apparatus more stably. With an increase in power consumption, in particular, a temperature regulating apparatus having high efficiency and very high temperature stability is required.
Some systems, which regulate the temperature of an apparatus having a heat-generating load by using a refrigerant, are based on a scheme of regulating the temperature of the refrigerant to a target temperature by regulating the flow rate of factory cooling water to a heat exchanger for performing heat exchange between the factory cooling water and the refrigerant. In this scheme, fluctuations in the temperature of the factory cooling water sometimes raise a problem. Japanese Patent Laid-Open No. 3-120153 discloses a technique of reducing the influence of such a problem. Japanese Patent Laid-Open No. 2006-031113 discloses a technique based on the consideration of changes in the overall heat transfer coefficient of a heat exchanger due to fluctuations in the flow rate of cooling water in addition to fluctuations in the temperature of factory cooling water.
According to Japanese Patent Laid-Open No. 3-102153, the degree of opening of a control valve that regulates the flow rate of cooling water is changed based on the difference between the target temperature of a refrigerant and the temperature of a refrigerant at the outlet of a heat exchanger, and the difference between the temperature of the refrigerant at the outlet of the heat exchanger and the temperature of cooling water at the inlet of the heat exchanger. However, the '153 document has no description about a specific method of determining the degree of opening of the control valve.
Japanese Patent Laid-Open No. 2006-031113 discloses a method of calculating the flow rate of cooling water necessary for heat exchange based on the target temperature of a refrigerant, the temperature of the refrigerant at the inlet of a heat exchanger, the temperature of cooling water at the inlet of the heat exchanger, and the overall heat transfer coefficient of the heat exchanger, and regulating the temperature of the refrigerant by regulating a control valve based on the flow rate. In this method, since the overall heat transfer coefficient of the heat exchanger changes in accordance with the flow rate of the cooling water, an overall heat transfer coefficient characteristic with respect to the flow rate of the cooling water is measured or calculated in advance, and a correction is made in accordance with the flow rate of the cooling water. However, the overall heat transfer coefficient also changes due to stains, or the like, in the heat exchanger, and the value of the overall heat transfer coefficient may change due to long-term use.